Recent years have seen a growing quantity of researches on a data storage apparatus that stores data by means of a movement of a magnetic domain wall. A micromagnetic region that forms a magnet may be referred to as a magnetic domain, and directions of magnetic moments as a result of an electron spin may be basically the same in the magnetic domain. A size and magnetic polarization of the magnetic domain can be properly controlled using a shape and a size of a magnetic material and external energy. A magnetic domain wall may refer to a boundary region between magnetic domains that have different magnetic polarization, and the magnetic domain wall can be moved by applying a magnetic field or a current to the magnetic material.
FIG. 1 shows a schematic structural diagram of a nano-magnetic track storage apparatus in the prior art. In FIG. 1, the apparatus includes a magnetic track 101, a writing unit 102, and a reading unit 103, where the magnetic track 101 includes multiple magnetic domains 104 and magnetic domain walls (not shown in the figure) between the magnetic domains. When an impulse current is applied to the magnetic track 101, the magnetic domain walls between the magnetic domains 104 are moved, and a movement of the magnetic domain walls causes a movement of the magnetic domains 104. In this case, the magnetic domains 104 move in an opposite direction of the impulse current. In a process of the movement of the magnetic domains 104, the writing unit 102 disposed on the magnetic track 101 applies a magnetic field to the magnetic domains 104. Under impact of the external magnetic field, an original magnetic field direction of the magnetic domains 104 rotates, and in this case, “0” or “1” can be recorded in the magnetic domains 104.
After information writing is completed, under impact of the impulse current, the magnetic domains 104 to which information is already written are moved to a position of the reading unit 103. The reading unit 103 is a magnetoresistive sensor, and the reading unit 103 includes a free layer and a pinning layer, where the pinning layer has a fixed magnetic field direction, and a direction of the free layer changes under impact of the external magnetic field. The free layer is relatively close to the magnetic track 101, and when the magnetic domains 104 pass by the reading unit 103, the magnetic field direction of the free layer changes under impact of a magnetic field in the magnetic domains 104. When the magnetic field direction of the free layer is consistent with the magnetic field direction of the pinning layer, the magnetoresistive sensor presents a low resistance state, and information read by the reading unit 103 in this case is “0”. When the magnetic field direction of the free layer is opposite to the magnetic field direction of the pinning layer, the magnetoresistive sensor presents a high resistance state, and information read by the reading unit 103 in this case is “1”. In this way, a process of writing information to and reading information from the magnetic track 101 is completed.
However, each magnetic domain 104 of the magnetic track 101 in the prior art can only store 1-bit information: “0” or “1”, causing low information storage density of the magnetic track.